I was getting IDEA errors on imports and other classes of the form "Cannot resolve symbol" although compilation was working fine. I have a multi-project build.sbt file with a multi-layered dependency hierarchy. I found that these errors only occurred for implicit, transitive dependencies. For example, if project A dependsOn project B and project B dependsOn project C, then I would get these errors in project C for classes in project A. If I add those dependencies explicitly, then the problem goes away (part in bold):